const mySymbol = (function () {
    let map = new Map()
    function fn() {
        if (this instanceof fn) {
            throw TypeError("cont new")
        }
        return {}
    }

    fn.for = function (key) {
        if (!map.has(key)) {
            map.set(key, {})
        }
        return map.get(key)
    }

    fn.forkey = function (val) {
        for (let [k, v] in map){
            if(val == v){
                return k
            }
        }
    }
    return fn;
})()